Keyhole saw might be your friend here. I actually have one where I broke MOST of the handle off so it fits smaller spaces :) For those in need, here is a picture of one: http://en.wikipedia.org/wiki/Keyhole_saw

I actually have a Dremel rotary and a multi-max (oscillating). The problem I had with the oscillating was I created more a friction fire than actual cutting LOL. I'll definitely try the routing bit.
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John GiottaMar 7 '11 at 19:05